I was once an avid mineral collector and one of my favorites was clear Fluorite. I recently picked up the two pieces below at a show but not just because they have clear Fluorite, they also have fossils in them. They come from a quarry in Walworth, NY that mines the Lockport formation (Silurian, Gorstian stage). The Lockport is a very hard, dolomitic limestone that is used as road gravel. The rock may be hard but it develops cavities from pressure solutions and ground water dissolving it away bit by bit. Within the cavities created by this process minerals can precipitate. Sometimes the cavities result from a fossil being dissolved away too.
This first piece has a large rounded cavity with some cubes of clear Fluorite. I can't be sure but some of the calcite druze looks like it is patterned after a bryozoan.
The second piece has a much more obvious fossil coral visible just below the mineral bearing pocket. It looks like a type of Favosite.
If you like mineral and want to see what else can be found in the Lockport Dolomite, head on over to the New York State Academy of Mineralogy website to see more.